必须通过服务器/应用程序/部分/设置层次结构，

using System;
using Microsoft.Web.Administration;

namespace CookieTimeout
{
    class Program
    {
        static void Main(string[] args)
        {
            // Get the server manager
            ServerManager serverManager = new ServerManager();

            // Get the app configuration
            Configuration config = serverManager.Sites["Default Web Site"].Applications["/App"].GetWebConfiguration();

            // Get the session state section
            ConfigurationSection sessionStateSection = config.GetSection("system.web/sessionState");

            // Set the cookie timeout to 20 minutes
            sessionStateSection["timeout"] = TimeSpan.FromMinutes(20);

            // Save the changes
            serverManager.CommitChanges();

            // Display a message
            Console.WriteLine("Cookie timeout set to 20 minutes);
        }
    }
}